<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .wwws {
            background-color: #754ef9;
            width: 3px;
            height: 45px;
            margin-top: 0px;
            transition: all .3s;
        }
        
        .wwws:hover {
            margin-bottom: 40px;
            height: 20px;
        }
    </style>
</head>

<body>
    <div class="wwws">

    </div>
</body>

</html>